"The fatal road incident occurred early on Tuesday some 20 to 30 minutes after midnight (around 2230 GMT Monday). Three other British soldiers were injured in the same accident," KFOR spokesman Colonel Yves Kermorvant said.
Police said a British military vehicle rolled off the road near the central town of Glogovac.
Kermorvant said 115 soldiers had lost their lives, mostly in accidents, since KFOR was deployed in Kosovo in 1999.